class_docstr: MixIn class to create a subclass with another indicator. The main line of
  that indicator will be substracted from the other base class main line
  creating an oscillator
  
  The usage is:
  
    - Class XXXOscillator(XXX, OscillatorMixIn)
  
  Formula:
    - XXX calculates lines[0]
    - osc = self.data - XXX.lines[0]
code: def __init__(self):
      self.lines[0] = self.data - self.lines[0]
      super(OscillatorMixIn, self).__init__()
  
file_path: backtrader/backtrader/indicators/oscillator.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import sys
  from .None import Indicator, MovingAverage
label_desc: Use image node_id 2 to create a new OscillatorMixIn object from inherited base classes: Indicator with example: obj = OscillatorMixIn()